it allows the same packages to run on any Linux kernel (any Linux distro). That is pretty useful.

flatpak itself depends on namespaces, so saying that it works on any kernel is quite a stretch.

Can flatpak do this? This is a GIMP3 appimage running on ubuntu 10.04 without any container:

The kernel is so old that even the appimage runtime itself complains of missing functions and has to fallback to a workaround.

UPDATE: flatpak can’t work because bubblewrap itself can’t:

PR_SET_NO_NEW_PRIVS is only available since kernel 3.5